Mobile terminals, such as mobile phones and tablet computers, currently use lithium batteries for power supply. Charging methods of the lithium batteries are generally classified into four stages that include trickle charging, pre-charging, constant current charging, and constant voltage charging. Since the constant current charging method uses a larger charging current, the lithium battery can be quickly charged and thus, decreasing charging time of the lithium battery. When lithium battery voltage reaches a safe cut-off voltage, the lithium battery is subjected to the constant voltage charging. In order to ensure safety of the lithium battery, the safe cut-off voltage is generally set as a fixed value and is lower than a safe voltage of the lithium battery. However, in an actual charging procedure, the lithium battery voltage measured by a power management chip is often higher than a real voltage of the lithium battery due to an internal resistance of the lithium battery. Thus, constant current charging time of the lithium battery is shorter, meanwhile constant voltage charging time of the lithium battery is extended, such that total charging time of the lithium battery is longer.